Dank Gravity
by Kakawot
Summary: Falling down the open manhole wasn't one of his smoothest moves, but Sonic never thought he'd get to meet green guys with pointy forks, let alone that they think his name has to do with a boombox.


**A/N: **I've been on a Sonic and TMNT binge lately, so of course my imagination combined the two into one bunny. My mind is efficient that way. English is not my first language, so if you come across anything weird, please let me know.

Enjoy!

* * *

Gravity acted a bit funny at high speeds. Or maybe the laws of physics didn't apply to Sonic, because he ran upside down in the sewer tunnels with no problem at all. It was far better than trudging in the sludge down below, which reeked horribly. He had accidentally fallen into an open manhole, not his smoothest move, but now that he was down here he might as well make the best of it. And so far, the dank network of the netherworld didn't disappoint.

Sonic tilted to the left to take a sharp turn, but even now his feet stayed glued to the ceiling of the nearly round tunnels. It reminded him of some landscapes back home, where he ran upside down as well, circling around whatever foe he was fighting at the time.

At least back home it didn't reek so bad.

Another left turn. Series of tubes mounted in the walls deposited their contents in the layer of water and god knows what else down below, but Sonic stayed above all that, keeping up his frantic pace. He wasn't running from or to anything. He just ran, laughing in gravity's face and making the laws of physics look the other way for a few brief minutes.

* * *

A blip registered on the scanner and disappeared so fast Donatello wasn't sure he had actually seen it. Nothing should move that fast. His eyes wandered from the project beneath his hands (reinforcing the TV remote) to the radar when it bleeped again. And again.

Something moved impossibly fast from checkpoint to checkpoint, throwing all of Donatello's radars for loops and it wouldn't be long before one of the semi-artificial intelligences monitoring the system would give up and commit electronic suicide.

"What in New York's stinky 34th street sewage line are we dealing with this time?" said Donatello to himself as he leaned over the defense system panel, tapping at the glass containing the radar readouts. It bleeped warnings as fast as it processed them, but the pattern seemed to be random. The anomaly drifted in and out of the scanning zone as if it was teasing the software. It disappeared for a full minute before it once again returned and crossed the scanners so often the radar sent out a continuous tone.

Sufficiently convinced that it wasn't a bug in the system Donatello sat down at his computer workstation and logged onto the surveillance system. His fingers missed the keys when Raphael appeared behind him and yelled at Donatello.

"Shut your machine up or I'll do it for you! I can't even hear the TV over your heart monitor!"

Donatello didn't bother swiveling around on his desk chair to face his brother. The bleeping continued, signaling that the unknown factor still raced around in the sewers.

"It's a warning system. Something triggered the radar, but it's moving too fast. I'm accessing the cameras as we speak," said Donatello calmly, and he entered the password correctly this time. All the monitors in his lab displayed the cameras mounted in the walls around the lair. Donatello studied them carefully, but Raphael saw it first.

"Look!" he cried, but by the time Donatello focused on the monitor it showed an empty sewer.

"Something moved," said Raphael, "a blur, but it was there."

Donatello eyed all the monitors, and this time he saw it as well. A blue… something slid in front of the camera and disappeared a heartbeat later. Donatello took a joystick out from under a heap of electronics and gently nudged the stick upwards. Some of the viewpoints moved, focusing on the ceiling.

"Made me some new cameras," explained Donatello for the sake of his brother. The blue blur moved from screen to screen, impossibly fast and agile.

"Maybe one of Stockman's robots," said Raphael, but Donatello shook his head.

"Nah, I've studied his robots. His are too bulky to achieve such a feat. And what's the use of creating a robot that runs around on the ceilings for ten minutes?"

Raphael got his sai out and twirled them.

"No idea, but I don't like it. I'm going out to say 'hi'."

"Yeah, and stab at it," said Donatello, but he retrieved his bo staff from where it leaned against the wall and followed his brother out the lair. Maybe he could poke at it.

* * *

It was a good thing Sonic didn't have epilepsy, because the frequent lights he flashed by would drop him with a seizure in ten seconds. If he looked at it properly, the sewers were a big obstacle course to play with. He bounced around the walls like a rubber ball and only scraped his knees twice, thanks to some rough plaster and a disagreement with a sign.

He only heard the rushing wind and water and his own breathing. No honking cars, screaming humans, or even the whining voice of a certain pink hedgehog. Just him and his abilities. And some human waste products, but Sonic wasn't terribly picky when it came to obstacle courses.

He hadn't encountered a living soul in this place. Not even an alligator showed up. He saw plenty of rats, but he expected that in the sewers. He'd be more freaked out if no furry animals showed themselves.

What he didn't expect, was two green beings stepping out from behind a wall and brandishing weapons at him. In a split second Sonic knew running past them wasn't an option, thanks to the sharp looking forks one of them held all the way up to the ceiling of the narrow tunnel. So Sonic leaned back and tore skid marks on the ceiling before dropping down to a slim sidewalk, wet with dubious water.

"Hi," he said cheerfully, and flashed his winning grin at the pair. The endorphin rush in his body forced him to grin and be happy with the world.

The fellows in front of him were quite strange. They weren't human, but as far as Sonic knew he and his gang were the only Mobians on this planet. But these… turtles, they looked like, could pass as Mobians with ease.

"Hi," said the one wearing a purple mask back, while the other one grunted.

"Who are you? _What_ are you?" asked purple turtle, and Sonic grinned even wider.

"I'm S to the O to the Nic, hedgehog by nature and awesome by style, pleased to meet you."

The two turtles shared a Look, but Sonic's endorphins made him not care at the moment. He wanted to keep on moving, running around until all his worries disappeared in the speed of being. He wobbled back and forth on the balls of his feet, hoping that the sewer water wouldn't make his shoes smell too badly.

"Hi, I'm Donatello, and this is Raphael," said purple turtle. The red turtle called Raphael grunted something, which Sonic, thanks to his experience with Knuckles, interpreted as 'nice to meet you as, I'm not good at this whole socializing shtick so I'll grunt and pretend to be cool'.

"I didn't know the Chaos Emeralds transported other Mobians to this place. Where are you from? Southern continent?"

Donatello lowered his red staff and cocked his head at the statement and question.

"I'm afraid I have no idea what you're talking about. We were mutated and grew up here. You're from another planet, then?"

Sonic did a spit-take. These guys actually _lived_ in the sewers and were mutants? He wasn't that surprised at the mutant bit, because a lot of weird creatures inhabited his home planet, but the sewers part got him.

"Yes, I'm from Mobius. Well, according to Tails, a friend of mine, it's more like another dimension of your planet. Or something, I don't know, I wasn't paying attention."

Raphael lowered his pointy forks, but kept his battle-ready stance.

"Been there, done that," he said. Donatello was more empathic.

"You got transported here? Need any help looking for the way home?"

Sonic shook his head, crossing his arms at the same time.

"Nah, we got it covered. We know what we have to do, it's a matter of _doing_ it," he said. "But thanks anyway."

"Alright, if that's what you want. Next question-"

Sonic held up a hand to silence the turtle. Now that he wasn't moving about the stench got to him, and these … mutants seemed to want to play Twenty Questions with him. It was interesting meeting these guys, and he wanted to hear their stories, but now wasn't the time.

For one, he was hungry. And second, he was getting tired, and he just met these guys. He was trusting by nature, but crashing on the couch of some unknown turtles in the sewers… yeah, not gonna happen. Donatello had a gleam in his eyes behind the purple band which Sonic knew all too well. Tails carried that same gleam when he had discovered something, and he'd sink his canine teeth in it and only let go when Sonic dragged him out of the workshop.

"One last question, and then I'm off. Sorry guys," said Sonic. Donatello pulled a downtrodden face at that, but he held his three-fingered hand to his non-existent chin as he thought. But Raphael beat him to it.

"How the hell do you move so damn fast?" he asked, and Sonic grinned and made a thumbs-up sign.

"Because I'm the fastest thing alive. Why else do you think my name is Sonic?"

Raphael shrugged.

"Maybe your parents really liked ghetto blasters."

Sonic's eye twitched. Naming someone after radio equipment?

"You didn't answer the question," said Donatello. "_How_ do you move so fast?"

It was Sonic's turn to shrug.

"I don't know, I just do. And no, my parents didn't like ghetto blasters; my name is Sonic because I can create sonic booms."

"That- that's not possible," said Donatello. "Every bone in your body would break at that kind speed, not to mention-"

Raphael slapped Donatello on his carapace, but the purple turtle kept on babbling. Raphael had to raise his voice to attract attention.

"Listen, Don. We've met aliens, we've fought robots and turned into dragons. IS a … blue fuzzy thing who can create sonic booms that special?"

Sonic bristled. Fuzzy thing? He was sleek and stylish, and certainly not a _thing_, thank you very much.

"I guess not," said Donatello, which made Sonic bristle even more. His ears flattened themselves in anger and his eyes narrowed.

"Look," he began, "I don't know who you guys are, or why you live in the sewers. But I'm not lying when I say I can move faster than the speed of sound."

"Prove it," challenged Raphael, crossing his arms, hands still grasping the pointy forks. Somehow he managed not to stab himself. That would be an embarrassing death, or so Sonic thought.

"Alright, but I'll need some room," said Sonic. "These sewers are too tight."

It was always cool to impress somebody with his speed, even sewer-dwelling mutant turtles. It might also be another excuse not to go home, where only more pink hedgehogs would be waiting for him. Not multiple hedgehogs, thankfully, one was more than enough.

"Hold on, I'll rig something up so we know you actually went faster than the speed of sound," said Donatello. "Be back in about ten minutes."

He abruptly turned and ran out of sight, but Sonic heard him splashing down tunnels a while longer. Finally his footsteps couldn't be discerned from the sound of flowing water and Sonic hopped from one foot to another. Had ten minutes already passed? Or was it more like one?

"So," began Raphael, and Sonic echoed the statement.

"You must have a hell of a story to tell," he said. "Who or what mutated you?"

Raphael threw his pointy fork up into the air and snatched it from mid-air, repeating this three or four times before switching to his other hand.

"Alien goo," he replied. "Got on us as tiny turtles, and we grew and got smart. Well, Donny got the biggest brains, but we can all talk and our master is a talking rat. Also got the alien goo on him."

Sonic swiveled his ears forward as something Raphael said required further investigation.

"'We?' There are more of you?"

Raphael almost missed catching his pointy fork, and he seized Sonic up as if deciding the blue hedgehog had the privilege to know.

"Yeah," he finally said. "Got two other brothers, but they're out tonight."

"Cool. But you don't seem that surprised to meet a giant talking hedgehog," said Sonic. Everybody reacted different to his appearance, but there were some common factors. Curiosity, fear and disbelief among them. But these guys were pretty laid-back about it, and Sonic wanted to know. He liked being a surprise, though the fear got old fast.

Raphael shrugged, once again tossing his pointy fork to the ceiling before catching it. He leaned back against the wall, his brown shell resting on the gross slime covering the walls.

"We've traveled to alien worlds, fight and are allied with other mutated beings, and so on. I'd be more surprised if you turned out to be a normal human being, making Donny's heart monitor beep that fast."

Sonic barked a laugh at that. Say what you want about sarcastic types, he had to laugh at their wit.

"Nice to be appreciated," he said. Raphael smirked at Sonic.

"My pleasure."

They talked some more about where Sonic was from (and what exactly he _was_) and what Raphael's weapons were called (sai, Sonic learned) until Donatello appeared again, a technical contraption in his hand. Sonic eyed the contraption, which looked suspiciously like a walkie-talkie.

"Here," said Donatello as he thrusted the thing at Sonic. "I rigged this up, it should measure your speed and can withstand high speeds, at least for a short while."

Sonic measured the weight of the thing in his hand. A digital readout showed him that he currently moved at zero miles per hour. It was heavy, but manageable.

"You _just_ rigged this up?" he asked, and Donatello grinned proudly. Sonic leveled a calculating look at the turtle before he copied the grin.

"I've got a friend who'd love to meet you. Think I mentioned him before, his name is Tails, and he's a mechanical genius. Never goes anywhere without a screwdriver."

Donatello fished a screwdriver from a leather thing which looked suspiciously like an utility belt.

"I think I'd like to meet him as well."

Sonic chuckled, but then it was time to get down to business.

"Well then, I'm off to break the sound barrier. For the seventh time today," he added. "It's a lucky number."

"Hold on, we'll grab our Battle Shell and travel with you for a bit," said Donatello. Raphael pulled a dubious face.

"Can't he just _go_ already and return with your walkie-talkie? There was a good show on-"

"No, this is Science, and for once you're going to be a part of it. Aren't you the least bit curious?" countered Donatello. Sonic knew by the emphasis the purple turtle lay on _science_ that it was an Important Word. Raphael sighed, threw the purple-banded turtle an annoyed look, but finally shrugged, as if to say: 'I'm not happy with this, but for the sake of brotherly peace I'll tag along and pretend to find something remotely interesting about this, despite the fact that I'm face to face with a giant blue talking hedgehog from another dimension, which in itself is rather interesting'.

Amazing, how good Sonic had gotten at interpreting body language of the grumpy-inclined (Knuckles, Shadow, to name a few).

"I don't think you can keep up with me in a Battle Shell, whatever it may be," said Sonic. Donatello smirked like Tails did when he knew something that Sonic didn't know, most likely in the mechanical realm.

"Oh, but _this_ Battle Shell will be able to keep up with you, until I run out of juice."

"Can't wait to see."

They agreed to meet up on the highway currently under construction, where Sonic would have fifteen free miles to achieve sonic speed. Sonic said that that was plenty of room to accelerate and decelerate safely, though Donatello had trouble believing that, or so he said.

* * *

It was a chilly night when all you did was stand still. Or hopping from one foot to another, what Sonic did in an attempt to ward off the biting cold which seeped under his fur. Spring and the accompanying sunshine was great, but the clear skies meant cold nights in the city of New York.

The fact that he only wore gloves and shoes wasn't helping any either, so he tucked his hands under his armpits in the faint hope that that would bring feeling back in them.

Sonic looked up when a two bright lights cut through the darkness and fell upon him. In a reflex Sonic jumped out of the way, but the lights slowed down and came to a stop a dozen feet away. With his eyes slowly adjusting he made out a big shape, but only when the driver cut the lights Sonic saw the vehicle in the ambient light.

The Battle Shell was not like Sonic had pictured it. He thought it'd be a van, painted green and with some sort of pun written on it. The vehicle _was_ painted green, but it looked more like an armored truck with lots of gizmos hanging off it. To Sonic it looked as fast as a snail on rollerblades: great in theory, until someone realized that snails don't have feet. The door opened and Donatello and Raphael jumped out, the former clutching a second walkie-talkie.

"Hope we didn't keep you waiting too long," said Donatello by way of greeting. Sonic wanted to say something about him always being early, but his teeth started chattering and wouldn't cooperate with his larynx. So he murmured something and flashed a confident grin.

"Nice van," said Sonic instead, keeping his teeth from chattering by sheer force of will. Donatello looked over his shoulder (and his shell) back at it and grinned.

"Thanks. Built it myself, actually. Well, more like modified it, but it's packing so much extra's an enemy doesn't want to touch it with a ten foot pole."

Sonic didn't doubt that. Tails could pack a lot of firepower in that small plane of his, and it had saved Sonic's life on more than one occasion.

"So we gonna do this or what?" said Raphael rather grumpy. His shivering was visible, and Sonic was glad that he had his fur to protect him.

"Keep your pants on, I'm mister Fast, with a capital F," replied Sonic. "On second thought, go put some pants on and keep them on, if you want the expression to make sense." He snapped his fingers. "Wait, I got it. Keep your mask on, right?"

The two turtles stared at him, before Raphael turned to Donatello.

"He reminds me of Mikey," he said. Donatello nodded sagely.

"Same babbling-"

"Hey!"

Sonic crossed his arms and pouted. He was _not_ babbling, he tried to make friendly conversation. He shrugged to himself. Oh well, their loss. He jogged in place to keep warm and swung the walkie-talkie back and forth.

"You ready to be amazed?" he asked, and the turtles stopped discussing this 'Mikey' person and focused on the hedgehog again.

"Show it, blue guy," said Raphael, and he and Donatello hopped back in the van. Bright lights once again blinded Sonic and he shielded his eyes automatically.

"Speedometer still showing a readout?" called Donatello, leaning out the window. Sonic checked the walkie-talkie thing. Some speedometer, he'd seen fancier equipment in his lifetime. Then again, these guys lived in the _sewers_ of all places. The zero on the readout turned from a zero to one and back, as if attempting to communicate in binary code. Must be from him jogging in place.

"All clear, green lights are a-okay, mission starting, want some other military phrase?" called Sonic back, and Donatello's head disappeared back inside the van. The monstrosity slowly rolled forwards and then started picking up speed.

Sonic took that as his cue to jog along, and he enjoyed the surprise on Donatello's face when they hit forty miles per hour and Sonic still ran alongside the van. Poor fools. He should've gotten them to bet on it, maybe he could have bought a chili dog on the way back. Too late for that now, he thought, and continued running alongside the van.

"I've hit top speed!" cried Donatello as they moved about sixty miles per hour. Sonic smirked and pulled ahead of the van, making sure the turtles got a good look at his backside. Because that's what they'd dream about tonight.

"Alright, see ya!" yelled Sonic over the roar of wind, but he wasn't sure if they heard him. It didn't matter. Running mattered.

He stretched out his arms behind him and turned his nose into the wind, bending his knees more. His classic running pose always felt like slipping into trusted old shoes. Sonic narrowed his eyes and then _really _took off, leaving the green van behind so fast it looked like a kid's toy in seconds.

He dared a glance at the walkie-talkie. The digits ran up so fast he could only make out the first number, and that steadily climbed from two to three to four hundred miles per hour in mere seconds.

To break the sound barrier he'd have to go faster, push more against the forces of nature holding him back, telling him that no hedgehog should be allowed in the special realm of soundlessness.

Five hundred. He'd have to accelerate more to break the sound barrier in time, or else he'd risk running into traffic once the road maintenance blockage stopped. He could probably dodge on time, but the wind he carried with him could make small cars swerve and crash. Sonic bent lower.

Six hundred. It always was a bit of a surprise to Sonic when all sound would leave his ears. Once Tails had started explaining something about density of gas and temperature and altitude to Sonic, but Sonic had fallen asleep at the speed of sound. He knew when he went faster than the speed of sound by experience, and never bothered calculating it. His legs would take him wherever he wanted to go how fast he wanted to go, so why bother with math?

Just a couple of miles of highway left, which only left Sonic six seconds to push harder. It'd be a tight fit and Sonic tried to look as far ahead as possible to look for ways to slow down.

But he _had _to make it to show those turtles. His pride as the fastest being on the planet was at stake!

* * *

"Seven hundred," said Donatello breathlessly. He had rigged up the second walkie-talkie to communicate with the first one, and it showed him the same readout. He parked the Battle Shell on the shoulder of an exit ramp, but left the engine running.

Raphael leaned across the center console and accidentally pressed a button, making the back compartment light up. Neither of them paid any attention to it. Donatello angled the speedometer so that Raphael saw the digits, and both of them went silent as the digits flew up so fast it was like the tiny hedgehog had turned into a Concorde.

"That's insane," said Raphael, but Donatello shushed him. Sonic had to be breaking the sound barrier right about now. With some mental calculations Donatello determined that the probable speed of sound at this altitude and temperature lay at 734 miles per hour, and Sonic rapidly approached that.

The digits halted for a second at 733 miles per hour, and Donatello cried out "no way!" when it suddenly sprang to 740, and continued to rise.

"He just did it?" asked Raphael, and Donatello nodded.

"I think so, by my calculations it's at seven hundred and forty three miles per hour, give or take. Simply amazing. He must have unbreakable bones or perhaps a force field to divert the air flow. Or-"

The clap of thunder interrupted him. But the skies were clear, so maybe it was more like the bang of a cannon, or a large gun going off.

It was the sound of speed.

Donatello smiled when he heard it. The blue guy hadn't lied, both his equipment and the sonic boom confirmed the truth.

"Hey! He's slowing down," said Raphael and jabbed at the speedometer. Donatello looked down and saw the digits drop from 770 miles per hour to 412 miles per hour within seconds, before dropping even further, thought at a more leisurely pace. It briefly lingered in the double digits before shooting back up to the triple, and Donatello knew that Sonic was on his way back.

Sonic's speed leveled out around the two hundred miles per hour, and Donatello started looking out the window to see if he noticed the hedgehog's approach.

"If he ran all the way to the end, he should be here in about four minutes," said Donatello for Raphael's sake. Donatello finally noticed the lights in the back of the Battle Shell and scowled at his brother as he slapped the button.

"Don't-" he began, but Raphael interrupted him in a bored tone.

"Press any buttons, because this thing has ejection seats, I know. Why did you even _make_ ejection seats in the first place? And shouldn't you make them bright red?"

"No," argued Donatello, "you know whenever someone says 'don't press the red button'? That's right, _someone always presses the red button_. And I don't want to scrape your shell of the side of the road and then heal you up again."

"Ah, but I'm a trained ninja, I can land on my feet."

Donatello turned in his seat to look at his brother skeptically.

"And what if we're driving on a bridge? Alongside a cliff?"

He let the silence and Raphael's imagination do its magic and grinned when Raphael arrived at the same conclusion Donatello had when he built the vehicle.

"Right, don't make a big red button, gotcha. Still-"

"So? Believe me yet?" called an impatient voice from outside the van. Donatello turned back and leaned out the window. He looked down onto the upturned face of Sonic, who wore such a broad grin Donatello was pretty sure the guy would suffer split mouth corners later.

"Yes," said Donatello simply, opened the door and stepped out. Raphael followed his example on the passenger side.

"Just _how _ can you run so fast when-"

"Wish I could tell you, turtleman, but I don't know. I just run and it all works out," interrupted Sonic. "I've been running my whole life. This wasn't even my top speed."

Donatello couldn't resist asking the blatant question.

"What us your top speed then?"

Sonic chuckled and put one hand on his hip, striking a confident pose.

"Don't know, haven't hit it yet."

This made Raphael bark a laugh and Donatello couldn't help but grin. He could learn to like this little guy.

"Here's your gizmo back," said Sonic, and handed the speedometer over to Donatello. "Thing works like a charm for something you just rigged up. Mind if I drop by and borrow it later?"

Donatello made a broad gesture and nodded.

"No problem." He hesitated. "Though we can't exactly contact each other easily."

Sonic shrugged and started hopping from one foot to another again. Raphael was beginning to shiver and Donatello felt the tendrils of cold take hold of his metabolism and slow it down.

"No problem," echoed Sonic. "I'll just start running around the sewers again and you'll notice me for sure."

Donatello made a mental note to install a speed camera in the sewers. Sonic stuck out his hand.

"It's getting late, cold, and I'm hungry, so I'll be heading home. Nice meeting you," he said. Donatello shook it and Sonic turned to Raphael. An idea occurred to Donatello and he scrambled back into the Battle Shell. Outside he heard his brother and the hedgehog exchange a few pleasantries, but Donatello interrupted that by calling out "hold on a sec!"

He plunged his hand into a compartment of the center console and found the treasure he had been looking for: a candy bar. Mikey always left food all over the van, much to Donatello's dismay, but in this case it was a good thing. Donatello let himself slide backwards out of the van and presented the candy bar to Sonic.

A second too late Donatello realized that he was standing in front of a being from another world, and sheepishly he said:

"I don't know if hedgehogs even like this, but I don't have any cat food in here. I'll bet it's a long way home for you."

At the mention of cat food Sonic pulled a disgusted face. Donatello couldn't help but wonder if the guy had tried some, since normal hedgehogs were known for liking cat food. Any human who came across a sentient hedgehog might assume it had the same diet.

"Don't worry, Earthen hedgehogs might not like chocolate, but this hedgehog does. Thanks!"

Sonic took the candy bar, unwrapped it and ate it in three bites.

"And yeah, I'm a long way from home, but that won't be a problem."

With a wink Sonic wiggled a foot and once again Donatello grinned.

"Safe trip home, Sonic, and I hope we'll see you soon, so I can introduce you to our two other brothers."

Raphael grunted a goodbye, and with a last wave Sonic sped off, leaving only footprints and a lingering sound behind, which had the potential to be 'see ya' or maybe 'sayonara' or even 'talk to you later, turtlemen'.

Donatello looked at the spot where Sonic had disappeared on the horizon and felt the grin which had frequented his face linger like Sonic's footprints.

As far as meetings with aliens from alternate dimensions went, he's had worse. A lot worse.


End file.
